Bicycle multi-gear cassette

ABSTRACT

A bicycle multi-gear cassette mountable to a wheel hub driver mechanism that includes truncated conical shell having a first opening proximate a small shell base and a second opening proximate a large shell base. The openings are coaxial with an axis of the shell. A plurality of toothed sprockets having different numbers of teeth are disposed on the shell and extend radially of the central axis. A torque load transmitting profile is configured on the shell proximate one of the small and large shell bases. A radial load transmitting profile is configured on the shell proximate one of the small and large shell bases. The shell, sprockets, and the load transmitting profiles embody a single piece.

BACKGROUND OF THE INVENTION

The present invention relates to bicycle multi-gear cassettes, and moreparticularly, to a multi-gear cassette that includes a truncated conicalshell, a plurality of toothed sprockets disposed thereon, a torque loadtransmitting profile, and a radial load transmitting profile wherein theshell, sprockets and load transmitting profiles embody a single piece.

In a conventional multi-gear bicycle cassette, a plurality of discretesprockets of variable diameter are arranged radially about an axis of awheel hub. Each sprocket has a plurality of teeth spaced around itsperiphery for engaging a bicycle chain. The sprockets are mountable tothe wheel hub to transfer pedaling forces from the bicycle chain to thewheel hub. In conventional designs, each sprocket may include a torqueand radial load transmitting profile that mates to a correspondingprofile on the wheel hub. One disadvantage of this design is that thesprockets are acting individually in transmitting pedaling load from thechain, at one end, to the wheel hub, at the other end, making thesprockets vulnerable to buckling and thus requiring thicker and heaviersprockets than desired.

In other devices, the individual sprockets may attached to a pluralityof carrier arms of an intermediate carrier, the arms receiving loadingfrom the sprockets and transmitting it to the wheel hub. Although thecarrier may provide some lateral support to the sprockets, the carrierarms may themselves twist and flex under loading, also leading tobuckling. Carriers with more rigid arms provide additional bucklingresistance but come with a weight penalty. Beyond being resistant tobuckling, carrier and noncarrier-based multi-gear cassettes must besufficiently rigid to resist excessive twisting and flexing under highimpact pedaling forces to provide positive and direct load transmissionto the wheel hub.

In the carrier cassettes described above, the discrete sprockets areattached to the carrier arms using bolts, mating threads, couplingprojections or the like. These mechanical connections not only requireadditional material on the mating pieces, making the sprocket assemblyheavier, but also introduce hole and thread features that weaken themating parts and provide possible fatigue and fracture failure points onboth the sprockets and carrier. Finally, such mechanical connectionsalso introduce additional unwanted flexibility as they twist and deformunder loading, softening load transmission from the chain to the wheelhub.

Accordingly, a single-piece cassette according to the present inventionavoids these design limitations by providing a rigid, buckling-resistantand lightweight load transmission path from the chain to the wheel hubdriver mechanism. In the prior devices having discrete sprockets, withor without intermediate carriers, the user may selectively replace oneor more of the individual sprockets to customize the gear ratios of thecassette. Additionally, in a cassette design with discrete sprockets,the complex recess and cutout features on the face of the sprockets, aswell as the precise chamfered tooth features, may be more readily andeconomically produced by stamping these features onto individualsprockets before assembly into a cassette. The present inventionachieves both a rigid and lightweight design that is contrary to theteachings of these prior devices. By using a single-piece truncatedhollow cone design that ignores the art-perceived need for discretesprockets, the present invention represents far more than a structuraldifference over these prior devices.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a lightweightsingle-piece multi-gear cassette that rigidly transmits load from thebicycle chain to the wheel hub.

The present invention provides a bicycle multi-gear cassette thatgenerally includes a truncated conical shell, a plurality of toothedsprockets of variable diameter, a torque load transmitting profile, anda radial load transmitting profile wherein the shell, sprockets and loadtransmitting profiles embody a single piece. The sprockets are disposedon the shell and extend radially of the shell axis. The shell has afirst opening proximate a small shell base and a second openingproximate a large shell base. The first and second openings are coaxialwith an axis of the shell. A torque load transmitting profile isconfigured on the shell at the small shell base, at the large shellbase, or at an axially-interior location on the shell proximate thesmall or large bases, or any combination thereof. Likewise, a radialload transmitting profile is configured at the small shell base, at thelarge shall base, or at an axially-interior location on the shellproximate the small or large bases, or any combination thereof. Theradial and torque load transmitting profiles are positioned on the shellto stably support the cassette when mounted on the wheel hub.

In one embodiment of the present invention, the shell may have a steppedconfiguration that includes a plurality of coaxial annular cylinders ofvariable diameter extending along the shell axis and a plurality ofcoaxial annular discs of variable diameter extending radially of theshell axis. The cylinders and discs are alternatingly arranged in astepped sequence. A torque load transmitting profile is configured at orproximate an axially-outermost cylinder or disc or any combinationthereof. Likewise, a radial load transmitting profile is configured ator proximate an axially-outermost cylinder or disc or any combinationthereof. The cylinders, discs, sprockets and load transmitting profilesembody a single piece.

In another embodiment of the present invention, the shell may have atapered configuration that includes a plurality of cone segmentsconnecting the toothed sprockets. One or more of the cone segments arepreferably oriented at an angle greater than 45 degrees from the shellaxis. The cone segments, sprockets and load transmitting profiles embodya single piece.

In another embodiment of the present invention, the bicycle multi-gearcassette may include a cap member that is coupled to or proximate thelarge shell base and extends radially of the shell axis. The cap memberincludes a third opening coaxial with the shell axis for receiving a hubdriver mechanism. The first opening proximate the small shell base isconfigured for receiving the hub driver mechanism. The torque loadtransmitting profile is configured at either the first or thirdopenings, or both, for transmitting torque load to the hub drivermechanism. The radial load transmitting profile is configured at eitherthe first or third openings, or both, for transmitting radial load tothe hub driver mechanism.

These and other features and advantages of the present invention will bemore fully understood from the following description of one or moreembodiments of the invention, taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a front perspective view of a bicycle multi-gear cassetteaccordance to one embodiment of the present invention;

FIG. 2 is a rear perspective view of the bicycle multi-gear cassette ofFIG. 1;

FIG. 3 is an exploded rear perspective view of the bicycle multi-gearcassette of FIG. 1 and a mating wheel hub;

FIG. 4 a is an exploded cross-sectional view of the bicycle multi-gearcassette of FIG. 1;

FIG. 4 b is an exploded cross-sectional view of an additional embodimentof the invention including a cap member attachable to interior portionof the shell;

FIG. 4 c is a cross-sectional view of an additional embodiment of abicycle multi-gear cassette showing a shell, sprockets, loadingtransmitting profiles and a cap member embodying a single piece;

FIG. 5 is an exploded cross-sectional view of an additional embodimentof a bicycle multi-gear cassette having a tapered shell;

FIG. 6 is a detailed cross-sectional view of a bicycle chain engaging asprocket tooth of the bicycle multi-gear cassette of FIG. 5; and

FIG. 7 is a detailed cross-sectional view of a bicycle chain engaging asprocket tooth of the bicycle multi-gear cassette of FIG. 1.

DETAILED DESCRIPTION

FIGS. 1-4 a and 7 illustrate a bicycle multi-gear or multi-sprocketcassette 10 according to one embodiment of the present invention. Thesprocket cassette 10 generally includes a shell 12, a plurality oftoothed sprockets 14, torque and radial load transmitting profiles 30,38, 46, wherein the shell 12, toothed sprockets 14 and load transmittingprofiles 30, 38, 46 embody a single piece. The single-piece constructionmay be achieved by any number of manufacturing processes, including forexample, forming, casting, forging, or machining. The toothed sprockets14 have different diameters and are disposed radially on the shell 12relative to the shell axis 18. Each sprocket 14 includes a plurality ofteeth 48 spaced around of the periphery of the sprocket 14 for engaginga bicycle chain 50 (FIGS. 6 and 7), each sprocket having a differentnumber of teeth.

In the embodiment shown, the shell 12 has a stepped configuration;however the shell may assume any linear or nonlinear shape that properlypositions the toothed sprockets. In the stepped embodiment shown, theshell 12 includes a plurality of coaxial annular cylinders 16 ofvariable diameter extending along a shell axis 18 and a plurality ofcoaxial annular discs 20 of variable diameter extending radially of theshell axis. The cylinders 16 and the discs 20 are alternatingly arrangedin a stepped sequence to form the conical shell 12.

The shell 12 further includes a first opening 22 at a small shell base24 and a second opening 26 at a large shell base 28. The first andsecond openings 22, 26 are coaxial with and substantially perpendicularto the shell axis 18. The shell 12 includes the torque and radial loadtransmitting profile 30 at the small shell base 24 on an inner surfaceof the shell 12 that engages a mating torque and radial transmittingprofile 32, in this embodiment mating projections, disposed on an outersurface on a hub driver mechanism 34 of a wheel hub 36. The torque andradial load transmitting profile 38 is also located at the large shellbase 28 on the inner surface of the shell that engages a mating loadtransmitting profile 40 on an outer surface of a removable cap member42. The cap member 42 extends radially of the shell axis 18. Inalternative embodiments, the cap member 42 may be coupled to a loadtransmitting profile disposed at an axially interior position of theshell 12 proximate the larger shell base 28 as shown in FIG. 4 b. Inalternative embodiments, torque and radial load transmitting profilesneed not exist at both the large and small shell bases 24, 28, so longas at least one torque load transmitting profile and at least one radialload transmitting profile exist on the shell 12. In an alternativeembodiment, the cap member 42, shell 12, sprockets 14 and loadtransmitting profiles 30, 38, 46 may embody a single piece as shown inFIG. 4 c. The cap member 42 includes a third opening 44 for receivingthe hub driver mechanism 34 therethrough. The cap member 42 furtherincludes a torque and radial load transmitting profile 46 at the thirdopening 44 on an inner surface of the cap member 42 that engages themating torque and radial transmitting profile 32 on the hub driver body34. Looking to the torque and radial transmitting profile 46 of the capmember 42, radial surfaces 41 transmit radial load to the hub drivermechanism 34, and torque surfaces 43 transmit torque load to the hubdriver mechanism 34. Torque and radial load transmitting profiles 30, 38on the shell 12 have similar radial and torque surfaces. In anembodiment where only a radial load is being transmitted through theload transmitting profile, torque surfaces 43 are eliminated.

In the embodiment of FIG. 5, a shell 52 includes a plurality of taperedcone segments 54 connecting the toothed sprockets 14 wherein the taperedcone segments 54, toothed sprockets 14 and load transmitting profiles30, 38, 46 embody a single piece. In a preferred embodiment, the taperedcone segments 54 form an angle θ greater than 45 degrees to provideincreased bending and buckling resistance to radially loading from thechain 50.

While this invention has been described by reference to particularembodiments, it should be understood that numerous changes could be madewithin the spirit and scope of the inventive concepts described.Accordingly, it is intended that the invention not be limited to thedisclosed embodiment, but that it have the full scope permitted by thelanguage of the following claims.

What is claimed:
 1. A bicycle multi-gear cassette mountable to a wheelhub, the cassette comprising: a truncated conical shell having a firstopening proximate a small shell base and a second opening proximate alame shell base, the openings coaxial with a central axis of the shell,the first opening proximate the small shell base receiving the wheelhub; a plurality of toothed sprockets having different numbers of teethdisposed on the shell and extending radially of the central axis; atorque load transmitting profile configured on the shell proximate oneof the small and lame shell bases; a first radial load transmittingprofile configured on the shell proximate the lame shell basetransmitting radial load to the wheel hub; a cap member extendingradially of the shell axis and non-rotatably coupled to the radial loadtransmitting profile proximate the lame shell base, the cap memberincluding a third opening coaxial with the shell axis and proximate thelame shell base, the third opening receiving the wheel hub; a secondradial load transmitting profile configured at the third openingtransmitting radial load to the wheel hub; and a third radial loadtransmitting profile configured at the first opening and transmittingradial load to the wheel hub, wherein the shell, sprockets, and thefirst and third load transmitting profiles are a single-piececonstruction; wherein the truncated conical shell comprises: a pluralityof coaxial annular cylinders of variable diameter extending along anaxis; a plurality of coaxial annular discs of variable diameterextending radially of the axis; and the cylinders and discsalternatingly arranged in a stepped sequence.
 2. A bicycle multi-gearcassette according to claim 1, wherein the torque load transmittingprofile is configured on one of the discs and cylinders, and the firstradial load transmitting profile is configured on one of the discs andcylinders.
 3. A bicycle multi-gear cassette according to claim 1,wherein one of the plurality of annular cylinders has a thicknesssmaller than a thickness of a base of an adjoining sprocket and one ofthe plurality of annular discs has a thickness smaller than thethickness of the base of the adjoining sprocket.
 4. A bicycle multi-gearcassette mountable to a wheel hub, the cassette comprising: a truncatedconical shell having a first opening proximate a small shell base and asecond opening proximate a lame shell base, the openings coaxial with acentral axis of the shell, the first opening proximate the small shellbase receiving the wheel hub; a plurality of toothed sprockets havingdifferent numbers of teeth disposed on the shell and extending radiallyof the central axis; a torque load transmitting profile configured onthe shell proximate one of the small and lame shell bases; a firstradial load transmitting profile configured on the shell proximate thelame shell base transmitting radial load to the wheel hub; a cap memberextending radially of the shell axis and non-rotatably coupled to theradial load transmitting profile proximate the lame shell base, the capmember including a third opening coaxial with the shell axis andproximate the lame shell base, the third opening receiving the wheelhub; a second radial load transmitting profile configured at the thirdopening transmitting radial load to the wheel hub; and a third radialload transmitting profile configured at the first opening andtransmitting radial load to the wheel hub, wherein the shell, sprockets,and the first and third load transmitting profiles are a single-piececonstruction; wherein the wheel hub includes a hub driver mechanism; andwherein the truncated conical shell comprises: a plurality of coaxialannular cylinders of variable diameter extending along an axis; aplurality of coaxial annular discs of variable diameter extendingradially of the axis; and the cylinders and discs alternatingly arrangedin a stepped sequence.
 5. A bicycle multi-gear cassette according toclaim 4, wherein the torque load transmitting profile is configured onone of the discs and cylinders, and the first radial load transmittingprofile is configured on one of the discs and cylinders.
 6. A bicyclemulti-gear cassette according to claim 4, wherein one of the pluralityof annular cylinders has a thickness smaller than a thickness of a baseof an adjoining sprocket and one of the plurality of annular discs has athickness smaller than the thickness of the base of the adjoiningsprocket.